The present application is directed to improvements in hammermills and, in particular, to improvements directed to enhancing the ability of hammermills to tear and commutate materials that are especially resistant to tearing such as tires and certain plastics, as well as other materials conventionally reduced by hammermills.
Hammermills have historically been utilized to reduce the size of or commutate a large number of materials. Conventional hammermills have been especially useful in reduction of highly frangible materials or materials that tear easily. For example, although cast iron, such as is used in engine blocks, would appear to be very strong and durable, this material is actually fairly frangible and relatively easy to break in a hammermill. Consequently, hammermills have frequently been used to shred automobiles or at least parts of automobiles.
However, conventional hammermills have been less effective in reducing materials that are not frangible and/or resistant to tearing. Examples of materials of this type are tires and certain plastics that are pliable and very tough, such that conventional beating by a hammermill merely bends or works the materials but does not break them. Other examples of problem materials include flexible sheet materials that tend to simply wrap about hammers and other hammermill components rather than being torn by the hammers. Materials of the latter type can include sheet aluminum and paper, for example.
Because of environmental and other changes, it is becoming increasingly important and economically viable to shred or commutate materials that have been historically difficult to reduce in a hammermill. For example, because worn tires have substantial disposal problems due to an ever decreasing amount of suitable landfill space and environmental restrictions on burning, alternative uses of such tires have been developed. These alternative uses included shredding tires to a fairly small particle size and then using the shredded particles in some type of construction. A typical use of shredded tires is as a component in the production of road construction materials, such as asphalt.
Disposal of medical wastes is another area in which environmental concerns have dictated major changes that limit simple dumping of the wastes. Often it is desirable to reduce the volume of medical waste for storage or transport to an area where destruction can occur. Such reduction would normally be a suitable task for a hammermill, but many components of medical waste are constructed of tough pliable plastics or rubbers that are not easily reduced in a conventional hammermill.
Consequently, it is desirable to have a hammermill construction that has improved ability to tear, cut and/or chew apart tough and pliable materials.
Certain other problems also arise out of trying to shred certain flexible materials in hammermills. One of these problems is that hammermills rotate at a relatively high rate of speed, thus producing a substantial air flow. Light materials may be carried or blown about the hammermill by the air flow so that the blown materials are never struck by the hammers and may block feed of new materials into the hammermill. Consequently, it is also desirable that construction of the hammermill restrict the flow of materials therein due to air currents.